kohler Memoirs Toilet, lousy warranty

We recently finished a major remodel. 1 Kohlers Memoir Toilet. comfort height K3453 (one piece unit) and 2 Toto's. I wish all 3 were totos. Memoirs now 2 yrs old and there is a very fine crack where the base and bowl meet along the underside bottom rt corner. Now not usable. Warranty only 1 yr, we are fighting with kohler but not having luck. Any suggestions how to get Kohler to replace?